1. Field of the Invention
The invention relates to an optical disc drive for controlling a wobble clock signal and a method thereof, and more particularly, to an optical disc drive which utilizes a protection mechanism to prevent the phase-frequency detector from wrongly determining a phase difference between the phase of the wobble clock and the phase of the wobble signal, and the method thereof.
2. Description of the Prior Art
In present day information society, storage of large amounts of information has become a major problem. Of all types of storage medium, the optical disc is one of the most useful mediums because of its high storage capacity and small physical volume. However, as multimedia technology progresses increased storage requirements are required, and the storing capacity of a normal CD optical disc (650 MB) is becoming increasingly less satisfactory. Therefore, a new optical disc standard, the digital versatile disc (DVD), with increased storage capacity has emerged. The physical size of a DVD is almost identical to that of a CD; however, the storage capacity of a DVD is much larger than that of a CD.
Up until recently, the DVD functioned only as a read-only multi-function digital disc; however, similar to the progress of CD-R and CD-RW discs and their ability to easily carry needed data, standards of the writable multi-function digital disc and the rewritable multi-function digital disc have been created. This enables users to utilize DVD-R and DVD-RW multi-function digital discs to store great amounts of data, in a manner similar to one used with the CD and CD-RW discs. As known by those skilled in the art, the writable multi-function digital disc and the rewritable multi-function digital disc can be divided into many standards, such as DVD+R multi-function digital disc and DVD+RW multi-function digital disc, which can be used in a common DVD-video player or a common DVD-ROM drive.
In order to manage the stored data, areas for storing data in the multi-function digital disc are divided into many frames, as they are in CD discs. The information of the multi-function digital disc is stored in every frame according to a certain regulation. Therefore, when writing information into a writable multi-function digital disc, the optical disc drive has to ensure the regulation of each frame of the multi-function digital disc so that data can be correctly written into the writable multi-function digital disc. For storing related information of each frame, multi-function digital disc has a special physical structure for addressing stored data. For a DVD+R writable multi-function digital disc or a DVD+RW rewritable multi-function digital disc, the information is an address in pregroove (ADIP). As known by those skilled in the art, the DVD+R disc and the DVD+RW disc both have wobble tracks to store the above-mentioned ADIP. Therefore, the DVD+R disc drive and the DVD+RW disc drive can read the wobble track to generate the wobble signal. Because the wobble signal stores the ADIP through phase modulation, the DVD+R disc drive and DVD+RW disc drive firstly have to generate a corresponding non-phase modulation wobble clock according to the wobble signal for a ADIP decoder to decode the wobble signal to obtain needed ADIP. In other words, if the wobble signal is unstable, the ADIP decoder cannot read needed ADIP from the wobble signal smoothly.